Railway hopper cars typically include one or more discharge openings through which lading within the car is adapted to be discharged by gravity. A discharge gate assembly including a frame is fitted to the hopper car and defines a discharge opening through which the lading within the car is exhausted. A gate is slidably mounted on the frame for movement between open and closed positions to control the discharge of the lading from the hopper car. The gate is typically moved between positions through a rack and pinion system, including two rows of racks welded to an underside of the gate and two pinions which are arranged on a rotatable operating shaft rotatably mounted on the frame of the gate assembly.
As will be appreciated, it is important to prevent inadvertent opening of the gate. Railway cars are subjected, however, to numerous impact forces, some of which can be quite severe. When a railway car moves down a hump in a classification yard, it likely will impact with other cars on the same track. A filled railway car weighs several tons and has a tendency to gather substantial momentum as it moves along the track. Thus, the impact with a stationary railway car to which it is to be coupled can be exceedingly forceful. While shock absorbers are built into the coupling units on the cars, severe shock loads remain within the body of the car and its contents. Such shock loads can affect the position of the gate. Of course, if a partially opened gate is not recognized, a substantial amount of lading can gravitationally pass through the gate as the cars move from one shipping location to another.
Accordingly, each gate assembly is typically provided with some form of locking mechanism for holding the gate in a closed position. The heretofore known locking mechanisms for holding the gate closed have a myriad of designs. Basically, however, such locking mechanisms include some form of mechanical locking members which are effective to lock the gate in a closed position, but they require both manual opening and manual closing to be effective.
For several reasons, the heretofore known manually operated locking mechanisms are constantly being destroyed when the gates are opened. The operating condition of the locking mechanism is often overlooked when lading is to be discharged from the hopper car. Limited visual access, inconvenient physical access, human error and the increasing demand to quickly unload the rail cars all contribute to the manually operated locking mechanisms being either substantially damaged or completely destroyed. Moreover, high-powered torque drivers are often used to open the gates and result in inadvertent destruction of the locking mechanisms.
Thus, there is a need and a desire for a rail car discharge gate assembly including a lock mechanism which securely maintains the gate in a closed position even under severe impact loading conditions and yet which opens automatically to avoid damage and destruction of the lock mechanism.